Date of Award

Summer 2019

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

School

Biological, Environmental, and Earth Sciences

Committee Chair

Kevin A. Kuehn

Committee Chair School

Biological, Environmental, and Earth Sciences

Committee Member 2

Micheal A. Davis

Committee Member 2 School

Biological, Environmental, and Earth Sciences

Committee Member 3

Jason D. Hoeksema

Abstract

Ectomycorrhizal (ECM) fungi are critical for the health of forest ecosystems where they can sequester large amounts of carbon in the form of soil organic matter, a matter of growing interest due to anthropogenic climate change. A clear understanding of their growth dynamics and responses to environmental changes is imperative for future work in forest management and the possible mitigation of increased atmospheric CO2. Six ECM fungal species were grown in liquid culture under varying nitrogen and phosphorus concentrations and ratios to assess how exogenous nutrient supplies affect fungal biomass stoichiometry and the degree of elemental homeostasis. Additional studies also examined nutrient and ratio effects on fungal ergosterol and chitin concentrations, which are important biochemical indicator molecules used to assess fungal biomass in environmental samples. Ergosterol and chitin concentrations in fungal dry mass differed significantly between species with no clear pattern. Unlike prior research on saprobic fungi, ECM fungal species displayed strict elemental homeostasis under varying resource nutrient conditions. Finally, seedlings of Monterey pine (Pinus radiata) were inoculated with the ECM fungus Rhizopogon occidentalis and grown in mycocosms to assess patterns of fungal growth, production and turnover. This controlled mycocosm approach resulted in lower estimations of production and turnover in comparison to field studies. These findings suggest future work with ECM could possibly benefit from a modified mycocosm approach in understanding how varying nutritional regimes influence fungal stoichiometry and what affect that could have on their potential to act as carbon sinks in properly managed forests.

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